STARCH. 123 
‘section with acetic acid and then with water, and finally 
adding iodine solution. ' 
Though the force with which starch appropriates iodine is 
‘quite considerable, it can, nevertheless, not be proved that the 
product is a chemical compound. Even dialysis, as also gen- 
tle warming, and even simple exposure to the air, is capable of 
eliminating the iodine from the compound. 
Only cellulose, under certain conditions, shares this behavior 
of starch to iodine. Beside lichenin (see Index), there is to be 
mentioned here also the amyloid of Schleiden, a form of cellu- 
lose which is capable of swelling, is colored blue by iodine, and 
occurs in the cotyledons of many of the Leguminose, for 
instance, in those of Zamarindus. Certain membranes of the 
hyphe of lichens also assume with iodine solution a blue color. 
The amount of amylum, even in such plants and parts of 
plants as are abundantly provided therewith, must necessarily 
be subject to great fluctuations when the before-mentioned 
function of starch as a reserve substance is taken into considera- 
tion. 
Potatoes and the rhizomes of the Maranta (Arrowroot) 
afford, for instance, from 9 to 26 per cent of amylum with ref- 
erence to air-dry substance, and Sarsaparilla is likewise a good 
example of the fact that the percentage of starch is very variable. 
The statements relating to the quantity of starch present in 
‘drugs can therefore be of value only under definite conditions. 
The size of starch granules is very variable, although, for the 
Same kind, remaining within narrow boundaries. The largest 
are found mostly in the underground receptacles of reserve sub- 
stances (Solanum tuberosum as much as 90 yu,’ Canna lanugi- 
nosa as much as 170 ), the smallest in the seeds of some 
Species of Acacia (about 1 y). 
An approximate representation of the relative dimensions is 
given by the following figures: | 
14 or mic. = micromillimeter = r/ya mm. = 0.000001 m. (compare 
Page 113), 
